This tiny island in the South Pacific may soon be completely uninhabitable, and it's all because the locals forgot to follow the Boy Scout motto: Be prepared. Since the turn of the 20th century, Nauru has been one of the world's prime sources for phosphate, a mineral compound formed over time from bird excrement, and an important ingredient in fertilizer. Phosphate mining quickly made Nauru rich, and at one point, the island even boasted the world's second-highest per capita GDP. But, as it turns out, basing your entire economy on dung can have its drawbacks.

For one thing, phosphate is a limited resource. By 2000, many believed the island's supply had dried up. In fact, all mining ceased until the government managed to hunt down the last few traces of the mineral in 2006. But the phosphate will soon be gone, leaving Nauru without a profitable export and without decent, farmable land. That's because phosphate runs in veins throughout the limestone and coral foundation of the island. To collect it, miners have to rip up the ground, leaving pillars and pits of less-valuable land behind. About four-fifths of the island is now ravaged to the point that no crops can grow and no one can inhabit it. Worse, the ruined landscape collects heat, which ends up creating a pattern of warm air that prevents rain clouds from forming. Currently, Nauru imports almost all its food and water, and there don't seem to be any industries poised to replace mining once the phosphate is gone.

The Dead Sea is famous for being the lowest point on Earth (an ear-popping 1,400 feet below sea level) and for being so salty that humans naturally float on top of it. But in recent years, it's also become famous for the tremendous rate at which it's evaporating. Currently, the Sea recedes about 3 feet each year, leaving ever-growing plains of salty, puckered, sinkhole-prone dirt in its wake. To really understand the phenomenon, tourists need only visit the Ein Gedi Spa. When it opened 20 years ago, you could step out the back door and be within a few feet of the salty water. But today, the Sea has receded so much that the trek to its shore amounts to a 1-mile hike.

The Dead Sea's imminent demise is also due to its neighbors' need for water. For the past several decades, Israelis, Palestinians, and Jordanians have been siphoning off more and more of the River Jordan -- the Dead Sea's primary water source. Growing populations and increased agriculture now require so much hydration that the Jordan is barely a trickle of its former self. Several solutions have been suggested, but the most promising is a canal that would funnel water from the Red Sea to the Middle East. The only problem is that the plan relies on Israel, Palestine, and Jordan engaging in long-term friendly relations -- something that may not happen in time to save the treasured landmark.

We've all felt that "sinking" feeling in the pit of our stomachs before, but imagine having it under the soles of your shoes -- all the time. That's part of life in Mexico City, which is built on the site of a former lake. In fact, the city was originally built on the lake, via a series of Aztec-designed aquatic platforms. Nifty as that was, the Spanish conquerors who tore through the land in the 16th century preferred a more traditional approach to urbanization, so they drained the lake and built a European-style city in the empty basin. Almost immediately, this proved to be a poor idea. Foundations sank into the soft clay and left many buildings tilting at odd angles.

That alone might have made Mexico City just a little eccentric -- charming, even. But as its population ballooned during the 20th century, the government had to search for new sources of water. Officials ended up pumping much of the city's supply out of the underground aquifer that had once fed the lake, which amounted to yet another bad idea. As the aquifer emptied, the soft clay above sank faster and deeper. In the past century, Mexico City has sunk more than 30 feet. Even worse, there's no clear, practical plan today for how to stop the droop and still provide water for the area's 22 million people. We suggest you run for the border with a camera and click some pics while you still can.

Don't get us wrong; in 20 years, there will still be Amish people, and there will still be places known as "Amish Country." But, chances are, both will be very different from their traditional versions.

The Amish, who originally emigrated from Europe in the 18th century, are most closely associated with farming and a technology-free lifestyle. And while the community has valued its isolation since the 1970s, those cultural norms have been shifting. The key culprit? The ever-skyrocketing price of land. Amish families typically have an average of seven children, which translates to a fast-growing population -- a population that's running out of room to expand. Because rural regions have become more popular with average Americans, many places that were farmland 20 years ago are now subdivisions, factories, and office complexes (not to mention a fair share of Amish Country tourist condos). Basically, the Amish need more land, but that land is now scarcer and more expensive.

So what's a separatist religious community to do? In many cases, the answer has been "become less separatist." Today, a majority of Amish don't rely on farming as their sole source of income. Many have side businesses, often connected with the tourism industry, and some Amish have even taken jobs in non-Amish owned factories, making the old life increasingly difficult to maintain.

The area now known as Freetown Christiania was originally a military base meant to defend one of the main waterways into the Danish capital of Copenhagen. But in 1971, it was captured by an invasion force nobody in the Danish military expected -- hippies.

At the time, the base wasn't being used, so it was pretty easy for a gaggle of unarmed characters to take over. Beyond simply staging a short-term sit-in, the group hunkered down for the long haul and declared the abandoned base its own autonomous country. With little resistance from Denmark's tolerant government, the residents of Christiania spent the next several years building a society where all property is collectively owned, all decisions are made by painstaking group consensus, and all marijuana is openly grown and sold. Through the years, the hippies became entrepreneurs as well -- founding businesses, opening cafes and music venues, and even inventing and marketing a transport bicycle perfect for moving large loads through Christiania's car-free streets.

Despite its status as one of Copenhagen's top tourist attractions, Christiania's days may be numbered. Since 2004, the newly elected conservative government has been cracking down on the hippie enclave -- first by staging a major drug bust and, more recently, by instituting a redevelopment plan for the land (which is still, technically, federal property). One major change tentatively approved by Christiania residents in April 2007 would turn the Citizen's Council into a regular public housing association and greatly increase rents. According to the Copenhagen Post, adult Christianians previously paid about $45 a month into a common fund to live there. Now, they'll have to pay the government closer to $800 a month. In addition, the plan gives the government the authority to tear down some hippie-built homes and replace them with (gasp!) condos.

When a landmark plays a part in one of the greatest novels of the 20th century, you know it's important. But U.S. Route 66 (or "The Mother Road," as John Steinbeck dubbed it in The Grapes of Wrath) has hardly gotten a retirement worthy of its stature. Completed in 1932 as the first well-marked road connecting Chicago to Los Angeles, Route 66 played an important role in Depression-era migration, World War II troop transports, and some seriously prosperous post-war tourism.

Unfortunately, the popularity of the road outpaced the maintenance of it. By the 1960s, it was both too small to handle modern loads of traffic and, in many places too beat up and potholed to be pleasant. As America transferred its wanderlust to the new, shiny, multi-lane superhighways, old Route 66 fell into even worse disrepair. The last section in regular use was bypassed by an interstate highway in the mid-1970s, and in 1985 the whole shebang was officially decommissioned by the federal government, which removed the road from most maps. Howebver, an estimated 80% of the original road is still driveable -if you can find it. Very little of what was once Route 66 is marked as such today. In some states, it's maintained as a scenic byway, but in other areas, it has become chunk of country road or city street. According to the Route 66 preserevation activist Fred M. Cain, there's even a 20-mile stretch in New Mexico that's still only covered in dirt and gravel.

Sad news for fans of tropical paradise: Nauru [see #1] isn't the only island nation in danger. The Maldives, a cluster of about 1,200 tiny islands off the coast of India, may completely vanish in fewer than 200 years. The problem? Well the Maldives are almost entirely flat. In fact the majority of the islands don't reach any higher than 3 or 4 feet above the Indian Ocean. Obviously, that means they're prone to occasional flooding, which is why the government has already built a 9-foot-high wall around the capital of Male. Recently, the situation has only gotten worse, thanks to the rising ocean levels associated with global warming. Maldivian officials currently estimate that the sea around them rises an average of 0.4 inches every year. That might not sound like much, but it adds up. The U.N.'s Intergovernmental Panel on Climate Change expects that, without any significant reduction in carbon dioxide emissions, ocean levels worldwide may rise by as much as 3 feet during the next century. Clearly, that's a problem for the Maldives. Since 2004, plans have been underway to evacuate several of the nation's flattest islands and shore up the land in its main population centers. Sadly, it's unlikely that these steps alone will save the country.

Don't tell Hemingway, but the 11,500-year-old glaciers that top Tanzania's Mount Kilimajaro may soon be nothing more than a memory. Since the 1880s, the Kilimanjaro ice cap has been melting at an alarming rate -a decrease of more than 80% since 1912 alone. In fact, Africa's tallest mountain could be ice-free by as early as 2015.

While the devastation couldn't be more obvious, the reasons behind it are more complicated than you might think. Equatorial temperatures are rising sharply, which is no doubt problematic for a lump of ice and snow that sits a mere 200 kilometers from the equator. But increased temperature probably doesn't deserve all the blame. Precipitation -or rather the lack thereof- is also taking its toll. The region around Kilimanjaro is becoming progressively more dry, so when glaciers melt, they aren't getting replenished as regularly. Not only that, but the sought will probably get worse before it gets better because deforestation on the mountain's slopes has created a hot microclimate. All of these problems have combined into a glacier-killing cycle, where deforestation blocks snowfall, increased temperatures hurry the melt along, and hot and thirsty locals increasingly turn to sources of income that cause deforestation.

The district of Diamer in northern Pakistan is currently home to one of the largest collection of petroglyphs in the world. Not impressed? Consider that many of these drawings, which are carved into rock surfaces, serve as ancient evidence documenting the advent and rise of Buddhism. Diamer is estimated to be home to more than 50,000 of these petroglyphs, all of which were created by local farmers and herders as well as travelers on the nearby Silk Road that connects the Middle East to China.

Although the artwork had survived more than 2,500 years of political and cultural change, it probably won't last another five. Diamer has been chosen as the location for a new, massive dam and reservoir system for Pakistan. Once built, it will provide water for the country's increased farming yields and generate electricity for millions of people. Unfortunately, according to archaeologist Harald Hauptmann, it will also obliterate any trace of the intricate and beautiful petroglyphs. In April 2007, Hauptmann told the German magazine Der Spiegel about his race against time in Diamer. He's attempting to record as many of the images as possible and plot their location on Google Earth. If he gets the funding he's after, he'll use lasers to scan the drawings and replicate them elsewhere. He's only got about two years to do this, and for obvious reasons, the Pakistani government is intent on building the much-needed structure. If completed to plan, the Diamer-Basha Dam will strip China's Three Gorges of the title of world's largest hydroelectric dam.

[ed. note: Construction on the dam began in 2011 and is expected to be completed in 2023.]

10. The Gettysburg Cyclorama

Sleek, spare, and sexy -that's the look internationally renowned architect Richard Neutra was going for when he unveiled his Cyclorama Center to the public in 1962. Opened just in time for the Civil War Centennial, the Center consisted of a sweeping, light-filled causeway that led to a large, drum-shaped white concrete building meant to house a 360-degree painting of the infamous Gettysburg battlefield.

Today, architects still regard the Cyclorama Center as some of Neutra's best work and a prime example of mid-20th century modernist design. However, the National Park Service appears to have a slightly less-than-favorable opinion. Nearby, construction is currently underway on a new home for the cyclorama painting -which means tearing down Neutra's master work. At present, it's estimated that the building will be razed no later than 2009. In the meantime, architecture lovers, historic preservationists, and local Gettysburg business owners have banded together to bring another fight to this already hallowed ground. Step one is mobilizing public support and awareness -accomplished most prominently when the Cyclorama Center was added to the World Monuments Watch List of 100 Most Endangered Sites in 2006. Step two is admittedly a little more confrontational, as it involves the long arm of the law. In December 2006, the Recent Past Preservation Network sued the federal government and alleged that the Park Service hadn't done enough to maintain the building and hadn't properly taken into account the impact the demolition would have on the surrounding environment. What happens next is anyone's guess, but given the Park Service is standing on their firm plan thus far, it might not be a good idea to wait before you visit.

[ed. note: In 2010, the court halted the demolition and ordered the Park Service to conduct an environmental impact study study. In August of 2012, the study recommended the building be torn down. It is currently standing but closed to the public.]

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The article above, written by Maggie Koerth-Baker, is from the July-August 2007 issue of mental_floss magazine. It is reprinted here with permission.

Hi Alice,No, I didn't miss the point. With a little more research you will learn that Saint Helena, currently only accessible by ship (5 days from Cape Town), is in the process of getting an airport. Flight via Ascension are severely limited, and mainly go to British officials. It is listed as one of the most remote communities on earth. Culture, habits, language (that is dialect - accent, they speak English) are going to change. Due to many factors (mostly economic) St. Helena has lost 1/3 of its population since 1999. Now with the introduction of air access there is the potential for more loss of culture through emigration and introduction of "off island" culture. I've been to St. Helena and care about the people I've met and the friends I've made. I want to see them prosper, but also fear that in doing so it may change the way of life they have always know. But I also know that their rich culture is something to be shared, and experienced. It is a tough balancing act.

I wholly agree with the St. Helena tip! If people would read about it online (including local sites), they'd be mesmerized at the complete isolation of the place. It has been on my wish list for a long time.

From Wikipedia's entry for Saint Helena: Saint Helena is one of the most remote islands in the world, has no commercial airports, and travel to the island is by ship only. A large military airfield is located on Ascension Island, with two Friday flights to RAF Brize Norton, England (as from September 2010). These RAF flights offer a limited number of seats to civilians.